<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS</title>
    <style>
        h2{
            color: chartreuse;
        }
    </style>
    <!--外部样式必须引入-->
    <link rel="stylesheet" href="my.css">
</head>
<!--style写在head是内部样式

-->
<body>

<h1 style="color: blue">CSS内联样式1</h1>
<h1 style="color: brown">CSS内联样式2</h1>

<h2 >CSS内部样式1</h2>
<h2 >CSS内部样式2</h2>
<h3>外部样式3</h3>
<h3>外部样式4</h3>
</body>
</html>